1. Field of the Invention
The present invention relates to a method for lining a tubular conduit with a tubular liner, which is composed of a tube of a nonwoven fabric impregnated with a thermosetting liquid resin and laminated both inner and outer faces with a highly airtight film.
2. Description of the Prior Art
When a tubular conduit, such as underground pipelines and passageways, becomes defective or too old to perform properly, the tubular conduit is repaired and rehabilitated without digging the earth to expose it and disassembling it into sections. This non-digging method of repairing an underground tubular conduit has been known and practiced commonly in the field of civil engineering. Typically, the method is disclosed by Japanese Provisional Patent Publication (Kokai) No. 60-242038.
According to this publication, this tubular conduit repair method comprises inserting a sufficiently long tubular flexible liner bag into the tubular conduit to be repaired by means of a pressurized fluid, like air and water. The tubular liner bag is made of a flexible resin-absorbent material layer impregnated with a thermosetting liquid resin, and has the outer surface covered with an impermeable plastic film.
More particularly, according to the publication, the tubular flexible liner bag is closed at one end and open at the other; the tubular flexible liner bag is first flattened. Then, the open end of the tubular liner bag is made to gape wide and hooked (anchored) at the end of the defective or old tubular conduit in a manner such that the wide-opened end of the liner bag completely and fixedly covers and closes the tubular conduit end; a portion of the liner bag is pushed into the tubular conduit such that an annular pocket is formed; then, the pressurized fluid is applied to the annular pocket of the tubular liner bag such that the fluid urges the tubular liner bag to enter the tubular conduit. Since one end of the tubular liner bag is hooked at the end of the tubular conduit, it remains there while the rest of the flexible liner bag is turned inside out as it proceeds deeper in the tubular conduit. (Hereinafter, this manner of insertion shall be called "everting" or "eversion".) When the entire length of the tubular liner bag is everted (i.e., turned inside out) into the tubular conduit, the everted tubular liner bag is pressed against the inner wall of the tubular conduit by the said pressurized fluid or by an inflatable pressure bag later inserted, and the tubular flexible liner bag is hardened as the thermosetting liquid resin impregnated through the tissue (thickness) of the liner bag is heated, which is effected by heating the fluid filling the tubular liner bag by means of a hot steam, etc. Thereafter the closed end of the liner bag is cut off. It is thus possible to line the inside wall of the defective or old tubular conduit with a rigid liner without digging the ground and disassembling the tubular conduit into sections.
Now, in the case of a sewer pipe, drain water is always running in the pipe so that, when a portion of the pipe is to be repaired by lining, it is necessary to divert the drain water to bypass that portion of the pipe. The most common manner to do so consists of plugging the pipe at a location upstream from the portion to be repaired so as to stop the flow of the drain water, pumping up the stopped drain water to the surface of ground (along a manhole), and sending it back to the pipe at a location downstream from the portion to be repaired (generally along the next manhole), thereby bypassing the portion of the pipe to be repaired.
However, the above-stated method of diverting the drain water to bypass the repair portion of the pipe is not always easy to practice; for example, if a road, a railway, or a river lies across the line connecting two manholes between which the pipe to be repaired extends, it is virtually impossible to set up a bypass passage for the drain water.
So, under such circumstances as described above where it was impossible to provide a bypass to divert the drain water, the flow of the drain water in the sewer pipe was temporarily checked (generally, for two to fifteen hours) at a location upstream from the portion to be repaired (for instance, at a pumping location), during which time the lining operation is conducted.
The Problems the Invention seeks to solve
Thus, in such conventional lining method, in order to accomplish the lining operation, it was necessary first to suspend the flow of the drain water and, only after then, the tubular liner bag is everted into the pipe by a fluid pressure, and it is heated while pressed against the inner wall of the pipe whereby the hardenable liquid resin impregnated through the tissue of the tubular liner bag is cured. Consequently, this lining operation was considerably time-consuming, especially so when the diameter of the pipe is large, such as 600 mm or greater, and hence the operation was costly.